The Connection Between Thyroid Disorders and Fertiltiy

July 1, 2020

Your thyroid gland is the butterfly-shaped organ in the front of your neck that produces hormones that regulate your body’s metabolism and affect vital functions. Fertility refers to a couple’s ability to conceive and bring a baby to term. The relationship between your thyroid health and fertility is an important and sometimes complex part of conception.

Thyroid Disorders

Thyroid disorders refer to a group of disorders that cause dysregulated functioning of the thyroid gland, resulting in the overproduction (hyperthyroidism) or underproduction (hypothyroidism) of thyroid hormones, triiodothyronine (T3), and thyroxine (T4).

The most common hypothyroid disorder is the autoimmune condition, Hashimoto's thyroiditis, which is predominant in women. Graves’ disease, another autoimmune condition, is the most common cause of hyperthyroidism.

How can thyroid disorders affect your fertility?

Hypothyroidism and hyperthyroidism can each negatively impact fertility—both the ability to become pregnant and the ability to carry a fetus to term. The presence of autoimmune antibodies, with or without hyper or hypothyroidism, can also impact your fertility.

Dr. Elena Christofides MD, FACE, and Fellow of the American Association of Clinical Endocrinologists, explains that “abnormal TSH levels can interfere with ovulation,” and that, “when you have any type of thyroid disorder (without proper management), you will see a luteal phase (the last half of the cycle after ovulation) disruption.”

This is mediated by progesterone levels. If a thyroid disorder is unregulated, a patient could have difficulty getting pregnant because there will not be implantation. You could also experience early miscarriage because of incomplete implantation.

Signs of low levels or misfunctioning of progesterone include:

  • A shorter or longer cycle than your typical menstrual cycle
  • Lighter or heavier bleeding than is typical for you
  • Longer or shorter windows for bleeding than is typical for you

Fertility is not a female-only concern. Thyroid disorders in men can also affect a couple’s fertility. Dysregulated thyroid function can damage sperm quality and motility, making it difficult for the sperm to enter the egg for implantation.

Hypothyroidism and Fertility

Too little thyroid hormone can impact fertility in the following ways:

  • Disruption of the menstrual cycle, making it harder to conceive.
  • Interference with the release of an egg from the ovaries (ovulation)
  • Increased risk of miscarriage
  • Increased risk of premature birth

Hypothyroidism is more common among women and can often be detected with a simple blood test of thyroid-stimulating hormone (TSH). Still, many women remain undiagnosed, especially women with ill-defined, subclinical hypothyroidism. Common symptoms of hypothyroidism include:

  • Frequent and heavy menstrual cycles
  • Fatigue
  • Muscle soreness
  • Forgetfulness
  • Dry skin and hair
  • Weight gain
  • Intolerance to cold

Subclinical hypothyroidism 

Subclinical hypothyroidism can be a controversial topic in the medical community. Dr. Christofides explains that subclinical hypothyroidism is meant to explain a clinical phenomenon, rather than a biological definition. Endocrinologist David Unuane MD, PhD says, “The upper limit of normal for TSH remains a matter of debate in literature. It is now widely accepted that this should be based on a population specific reference range.”

Many doctors are hesitant to treat, or even acknowledge subclinical hypothyroidism. Scott Isaacs, MD, FACP, FACE, cautions against a tendency to overtreat and emphasizes managing your thyroid condition with the care of a trusted specialist.

Evidence regarding the efficacy of treatment for subclinical hypothyroid disorder remains specific to both the qualitative and quantitative symptoms of each person, especially regarding fertility.

Dr. Christofides works on a patient-to-patient basis. For a patient with subclinical hypothyroidism, Dr. Christofides begins with a comprehensive screening of metabolic syndromes that could also cause fertility problems.

“If I find no other metabolic disorders, I will give patients a trial therapy of levothyroxine for three months. We will then document and measure to discern if the treatment is corrective,” explains Dr. Christofides. If the treatment shows qualitative and quantitative improvements, Dr. Christofides will continue the patient on treatment to regulate their condition.


The autoimmune condition Graves’ disease is the most common cause of hyperthyroidism. Too much thyroid hormone caused by hyperthyroidism can affect fertility by:

  • Disrupting the menstrual cycle
  • Causing a reduction in sperm count
  • Increasing the risk of early-term miscarriage
  • Increasing the risk for premature birth

Patients with hyperthyroidism are typically kept on the lowest effective dose of their medication during pregnancy because these medications can cross the placenta. If you have a history of Graves’ disease, it is important to communicate with your doctor, even if your condition is under control.

Autoimmunity, inflammation, and fertility

Autoimmunity can negatively affect fertility, even when TSH levels are within normal range. Dr. Unuane explains that the immune imbalance indicated by thyroid antibodies can impact fertility by:

  • Causing difficulty with fertilization of the egg
  • Causing difficulty with implantation
  • Increasing the risk for miscarriage

Specialists don’t always agree on whether or not your antibody count is an important factor. Dr. Christofides explains that while the antibody count does not matter for diagnosis (the presence of any level of thyroid antibodies indicates an autoimmune condition) the antibody count can be clinically significant.

Because both the presence of antibodies and thyroid hormone levels play an important role in fertility, it is important to work with your doctor to achieve a stable balance, based on your individual needs.

Lifestyle interventions

Dr. Christofides explains quite simply, “Your body is looking for indicators that you are healthy and fit enough to carry a child.” This means that a healthful diet and being physically active may help. “You don’t have to be a bodybuilder,” Christofides says, “but it is good to balance between cardiovascular activities and resistance training.”

Dr. Christofides advocates an autoimmune diet protocol. There are a few different diets that focus on being anti-inflammatory to treat autoimmune conditions, and you can choose one that works best for you. Avoiding artificial additives and processed food is a big component.

Researchers are also finding that certain nutrients may have a preventative effect on developing autoimmune thyroid disorders. This can be important information for people who are planning a pregnancy, especially those with a family history of autoimmune conditions.

Vitamin D can also play a role in keeping your thyroid healthy. Some recent studies show promising results that vitamin D may also help to lower thyroid antibodies. Vitamin D is easy to find in supplement form (if you aren’t getting enough from the sun). 

Selenium is another important nutrient for thyroid health. Supplementing with selenium can be a bit trickier, and Christofides recommends getting the nutrient from your diet. Macadamia nuts are an excellent source.

Work with your endocrinologist

Yes, thyroid conditions can complicate fertility, but they absolutely do not make it impossible. First and foremost, properly regulating your thyroid levels will usually solve fertility issues that are linked to your thyroid. Autoimmune conditions can complicate pregnancy, but not always, and there is plenty you can do to make your body a healthier, more balanced system. Remember that each case is individual. Find a thyroid specialist, and then develop an approach that works for you and your individual needs.



Share this blog post